I've almost got rid of a few over the years thinking it was a male based on a tiny preflower that hadn't developed yet. I just wanted to make sure you didn't jump the gun and throw out a perfectly good female. I've had a fem seed that was a true hermi, it had a all the care and attention in the world and still popped out some balls. I've heard and read that fem seeds are more prone to this, and it makes sense to an extent. Fem seeds are made by causing a female to hermi and self pollenate resulting in an offspring carrying only the genes of the mother. Still possible to get a male, but unlikely.. I guess your the unlucky one.
